BACKGROUND Legionnaires' disease is one of the most common types of community-acquired pneumonia. It can cause acute kidney injury and also occasionally become severe enough to require continuous renal replacement therapy (CRRT). Non-occlusive mesenteric ischemia (NOMI) is a condition characterized by ischemia and necrosis of the intestinal tract without organic obstruction of the mesenteric vessels and is known to have a high mortality rate. CASE REPORT A 72-year-old man with fatigue and dyspnea was diagnosed with Legionnaires' disease after a positive result in the Legionella urinary antigen test pneumonia confirmed by chest radiography and computed tomography. He developed acute kidney injury, with anuria, rhabdomyolysis, septic shock, respiratory failure, and metabolic acidosis. We initiated treatment with antibiotics, catecholamines, mechanical ventilation, CRRT, steroid therapy, and endotoxin absorption therapy in the Intensive Care Unit. Despite ongoing CRRT, metabolic acidosis did not improve. The patient was unresponsive to treatment and died 5 days after admission. The autopsy revealed myoglobin nephropathy, multiple organ failure, and NOMI. CONCLUSIONS We report a fatal case of Legionnaires' disease complicated by rhabdomyolysis, acute kidney injury, myoglobin cast nephropathy, and NOMI. Legionella pneumonia complicated by acute kidney injury is associated with a high mortality rate. In the present case, this may have been further exacerbated by the complication of NOMI. In our clinical practice, CRRT is a treatment option for septic shock complicated by acute kidney injury. Thus, it is crucial to suspect the presence of NOMI when persistent metabolic acidosis is observed, despite continuous CRRT treatment.